##Setting up CanCan 1 : Ruby 2 : Devise 3 : Rails 4

This guide was created partially following Tony Amoyal's tutorial [here.] (http://www.tonyamoyal.com/2010/07/28/rails-authentication-with-devise-and-cancan-customizing-devise-controllers)

######Create a new app:

rails new app
bundle install

######Install Devise:

gem 'devise'
bundle install

rails generate devise:install
rails generate devise user

######Install CanCan:

gem 'cancan'
bundle install

rails generate cancan:ability

rails generate model role name:string

rails generate migration UsersHaveAndBelongToManyRoles

######Edit the migration

class UsersHaveAndBelongToManyRoles < ActiveRecord::Migration 
  def self up 
    create_table :roles_users , :id => false do | t | 
      t. references :role , :user 
    end 
  end 

  def self down 
    drop_table :roles_users 
  end 
end 

rake db:migrate

######Edit User model

class User < ActiveRecord::Base 
  has_and_belongs_to_many :roles 
  def role? ( role ) 
    return !! self roles find_by_name ( role. to_s camelize ) 
  end 

######Edit Role model

class Role < ActiveRecord::Base 
  has_and_belongs_to_many :users 
end 

######Edit Ability model

class Ability
  include CanCan::Ability 

  def initialize ( user ) 
    user || = User. new # guest user 

    if user. role :super_admin 
      can :manage , :all 
    elsif user. role :product_admin 
      can :manage , [ Product, Asset, Issue ] 
    elsif user. role :product_team 
      can :read , [ Product, Asset ] 
      # manage products, assets he owns 
      can :manage , Product do | product | 
        product. try ( :owner ) == user
      end 
      can :manage , Asset do | asset | 
        asset. assetable try ( :owner ) == user
      end 
    end 
  end 
end 

mkdir app/controllers/users
vi app /controllers/users/registrations_controller. rb 

######Edit RegistrationsController

class Users::RegistrationsController < Devise::RegistrationsController 
  before_filter :check_permissions , :only => [ : new , :create , :cancel ] 
  skip_before_filter :require_no_authentication 
  def check_permissions
    authorize! :create , resource
  end 
end 

######Edit config/routes.rb and replace devise_for :users with:

devise_for :users , :controllers => { :registrations => "users/registrations" } 

######Edit ApplicationController

class ApplicationController < ActionController::Base 
  ...
  rescue_from CanCan::AccessDenied do | exception | 
    flash [ :error ] = exception. message 
    redirect_to root_url
  end 
  ...
end 

######Add WelcomeController

rails generate controller welcome#index

######Navigating to /users/sign_up will now redirect you to welcome #index

######Resources: http://www.tonyamoyal.com/2010/07/28/rails-authentication-with-devise-and-cancan-customizing-devise-controllers